Implantable medical devices for treating irregular contractions of the heart with electrical stimuli are well known in the art. Some of the most common forms of such implantable devices are defibrillators and pacemakers. Various types of electrical leads for defibrillators and pacemakers have been suggested in the prior art.
A broad group of leads may be characterized by the fact that they are placed transvenously. These leads are introduced into the patient's vasculature at a venous access site and travel through veins to the locations where the leads' electrodes will implant in or otherwise contact coronary tissue. One large subfamily of the group of transvenously-placed leads are those that are implanted in the endocardium (the tissue lining the inside of the heart) of the right atrium or ventricle. Another subfamily of the group of transvenously-placed leads are those that are placed in the branch vessels of the coronary venous system to stimulate the left ventricle.
The treatment of heart failure often requires left ventricular stimulation either alone or in conjunction with right ventricular stimulation. For example, cardiac resynchronization therapy (also commonly referred to as biventricular pacing) is an emerging treatment for heart failure, which requires stimulation of both the right and the left ventricle to increase cardiac output. Left ventricular stimulation requires placement of a lead in or on the left ventricle in the lateral or posterior-lateral aspect/region of the heart. One technique for left ventricular lead placement is to advance a lead endovenously into the coronary sinus and then advance the lead through a branch vein onto the surface of the left ventricle so as to stimulate the myocardium of the heart. Although methods and tools have been developed to navigate the lead through the vasculature, and in particular to direct the lead into a selected branch vessel of the coronary sinus, it can be difficult to orient the electrodes to face and stimulate the myocardium. If the electrodes come into contact with the pericardial wall portion of the branch vessel, rather than the myocardial wall portion, a degraded site for sensing and pacing may result.
The left ventricle beats forcefully as it pumps oxygenated blood throughout the body. Repetitive beating of the heart, in combination with patient movement, can sometimes dislodge the lead from the branch vessel. Over time, the electrodes may lose contact with the heart muscle, or move from their original location and orientation.
There is a need for an improved lead and method of implantation for orienting the lead into the coronary sinus branch vessels such that the lead electrodes contact the myocardium, and also to provide controlled fixation and removal of the lead.